An odorless silicone compound, a method of preparing a cosmetic material containing it, and a modified silicone compound comprising a branch polymer comprising a hydrophilic group.
1. Field of the Invention
This invention relates to a purified, modified silicone compound which has very little odor over time even when blended in an aqueous system, and to a method of manufacturing a cosmetic material containing same and a modified silicone compound comprising a branch polymer comprising a hydrophilic group.
2. Background of the Invention
Conventionally, modified silicone compounds were manufactured by carrying out an addition reaction between a hydrogen siloxane and a compound with a terminal double bond in the presence of a precious metal catalyst such as platinum hydrochloride. However, since an odor was acquired with time when a polyether modified silicone obtained in this way was used in an emulsification system, it was difficult to use in cosmetics.
Describing this mechanism, in a polyether modified silicone compound, the polyether modified silicone will suffer oxidative degradation with time, generating formaldehyde and acetaldehyde.
That is, for example, when an allyl etherated polyether is used as a polyoxyalkylene, when the addition reaction between this and hydrogen siloxane is performed in the presence of a platinum catalyst, the allyl group undergoes an internal shift as a side reaction, generating propenyl etherated polyether. As this propenyl etherated polyether does not react with hydrogen siloxane, it remains as an impurity in the polyether modified silicone produced by the normal addition reaction, and unreacted allyl etherated polyether also remains in the polyether as an impurity. Moreover, it isomerizes gradually due to the remaining platinum catalyst, and unreacted allyl etherated polyether becomes propenyl etherated polyether. Therefore, if water acts on the polyether modified silicone containing these impurities, cleavage of the propenyl ether will occur, generating propionaldehyde and a foul odor. This reaction is promoted by acids, and the reaction velocity increases the lower the pH.
JP App. No. 01-123053, based on the elucidation of the aforesaid second odor-causing mechanism, discloses that under certain conditions, in an aqueous solution of pH 7 or less, an odorous substance was generated by treating a polyether modified silicone containing the above-mentioned impurities until the degree of unsaturated bonds in the residual double bond containing polyether in the polyether modified silicone became 0.002 or less, and when this was removed, the polyether modified silicone no longer caused a foul odor even after time had elapsed.
However, the following problems occur with the above-mentioned acid solution. Specifically, the reaction of hydrogen siloxane and allyl etherated polyether is not always the same. The allyl etherated polyether content which remains, changes when the rate of the addition reaction changes, and the propenyl etherated polyether content also changes. Therefore, the required reaction time and concentration of acid solution differ for every batch. Moreover, there is a difference in the rate of hydrolysis between allyl etherated polyether and propenyl etherated polyether. Under the same reaction conditions, as the hydrolysis rate of allyl etherated polyether is slow, allyl etherated polyether remains, propenyl etherated polyether is produced with time, and substances with a foul odor are generated.
If chlorination is performed under rigorous conditions to hydrolyze the allylated ether, the polyoxyalkylene group is oxidized and a foul odor is again produced.
As a means to solve the batch difference due to the reaction rate, U.S. Pat. No. 5,225,509 and JP 7-330907 disclose a method of hydrogenating the unsaturated double bonds by a hydrogen addition reaction. This method is not based on the difference between allyl dietherated polyether and propenyl etherated polyether, and may be expected to permit hydrogenation of the unsaturated double bonds so that the generation of propionaldehyde can be stably controlled.
However, when this researcher carried out studies to manufacture a more stable modified silicone, he discovered that with a hydrogen addition reaction alone, aldehyde condensation products such as acetal, paraldehyde and aldole remain, producing aldehyde in solution and causing a foul odor. As these compounds do not have unsaturated bonds in the molecule, they cannot be removed at all by the hydrogen addition reaction. Moreover, as they do not have unsaturated bonds, it is ineffectual to control the degree of unsaturation.
The generation of a foul odor by such aldehyde condensation products was not disclosed by either of the above patents, their chief aim being focused on treating the unreacted, unsaturated groups containing polyether.
The inventors found that by performing hydrogen addition processing on a modified silicone having a hydrophilic group as branch polymer, and carrying out the reaction at pH 7 or less, the foul odor due to aldehyde condensation products of this modified silicone can be prevented, and they thereby arrived at the present invention.
It is therefore a first object of this invention to provide a modified silicone which has a hydrophilic group as branch polymer, and which does not produce a foul odor with time.
It is a second object of this invention to provide a cosmetic material which uses a modified silicone having a hydrophilic group as branch polymer, and which does not produce a foul odor with time.
It is a third object of this invention to provide a method of purifying the modified silicone having a hydrophilic group as branch polymer.
This invention is related to a modified silicone compound having a branch polymer comprising a hydrophilic group synthesized by an addition reaction of an organohydrogen polysiloxane and at least one type of compound chosen from an alkenylated polyoxyalkylene compound, alkenylated glycerine compound and alkenylated sugar in the presence of a platinum catalyst or rhodium catalyst, and which contains a hydrophilic group. In this compound, unsaturated bonds which remain after performing a hydrogen addition reaction on the reaction solution after the above-mentioned addition reaction, are hydrogenated. Subsequently, aldehyde condensation products which remain in the silicone are decomposed by treating with an aqueous solution of pH 7 or less containing an acidic substance as reagent, or they can be decomposed by treating the propenyl etherated polyether in the reaction solution after the above addition reaction, using an aqueous solution of pH 7 or less containing an acidic substance as reagent. Then, the above-mentioned modified silicone compound is purified by hydrogenated the aldehyde and the alkenylated ether compound purified by the hydrogen addition reaction. The odorless modified silicone compound, and the cosmetic materials prepared from it, are characterized in that the degree (meq/g) of unsaturation of this modified silicone compound is 0.002 or less overall, and the amount of aldehyde produced by heat aging at 50xc2x0 C. for 0.5 hours in 0.23N hydrochloric acid is 70 ppm or less.
The modified silicone compound which comprises an organopolysiloxane having a branch polymer comprising the above-mentioned hydrophilic group, is represented by the following general formula (1):
R1aR2bSiO(4-a-b)/2xe2x80x83xe2x80x83(1) 
In the above formula, R1 are identical or different organic groups chosen from an alkyl group with 1-30 carbon atoms, an aryl group, an aralkyl group, a fluorosubstituted alkyl group or an organic group represented by the general formula (2):
xe2x80x94CmH2mxe2x80x94Oxe2x80x94(C2H4O)c(C3H6O)dR3xe2x80x83xe2x80x83(2) 
where R3 is a hydrocarbon group having 5-30 carbon atoms, or an organic group represented by R4xe2x80x94(CO)xe2x80x94 (in the formula, R4 is a hydrocarbon group with 1-30 carbon atoms.)
c, d, and m are integers in the range 0xe2x89xa6cxe2x89xa650, 0xe2x89xa6dxe2x89xa650 and 0xe2x89xa6mxe2x89xa615, respectively. R2 is a hydrophilic group represented by the following general formula (3).
xe2x80x94Qxe2x80x94Oxe2x80x94Xxe2x80x83xe2x80x83(3) 
(in the formula, Q is a divalent hydrocarbon group with 3-20 carbon atoms which may contain at least one of an ether bond or ester bond, and X is a monovalent hydrophilic group chosen from polyoxyalkylene, glycerin, and sugar). a and b are given by 1.0xe2x89xa6axe2x89xa62.5 and 0.001xe2x89xa6bxe2x89xa61.5, respectively.